Seeing double: shock waves and the de Sitter horizon

TL;DR

This paper studies how a particle near a de Sitter horizon creates shock waves and horizon deformations, revealing insights into holography and horizon dynamics in cosmological spacetimes.

Contribution

It introduces a model of particle-induced shock waves in de Sitter space and analyzes their effects on the horizon, providing new holographic interpretations.

Findings

Particle displacement causes horizon deformation with parity violation.

Shock wave limit restores horizon symmetry and implies a particle from the static patch.

No extension of the holographic screen is needed to explain the signal.

Abstract

We consider a de Sitter observer in his rest frame at late times who observes a particle slightly displaced from unstable equilibrium. Initially, the observer notices an axisymmetric and parity-violating deformation along the trajectory of the displaced particle of his cosmological horizon. On a time scale of order $\ell$, the de Sitter radius, the particle is nearly absorbed by the cosmological horizon and has been accelerated to an ultra-relativistic speed and thus is well approximated as a shock wave. In the shock wave limit, the observer sees an axisymmetric deformation of his horizon with parity restored, which we interpret as arising due to a particle from the complementary static patch. We comment on the holographic implications of this result and note that there is no need to extend the holographic screen of de Sitter spacetime beyond the empty static patch to account for this signal.